Abstract
Calculations of the nuclear magnetic resonance chemical-shielding tensors of a suite of mercury-containing materials using various cluster models for the structures provide a stringent test of the procedures for forming models and for calculation with various methods. The inclusion of higher co-ordination shells in the molecular clusters permits quantum chemical calculations of (199)Hg chemical-shielding tensor elements within 3% of the experimental values. We show that it is possible to reduce the size of computationally expensive molecular-cluster calculations with limited effect on calculated NMR parameters by carefully introducing the frozen core approximation. The importance of the relativistic Hamiltonian for accurate predictions of chemical-shielding values is demonstrated within the molecular cluster approach. The results demonstrate that careful design of a cluster to represent the solid-state structure, inclusion of relativistic components in the Hamiltonian at least at the spin-orbit level, and judicious use of approximations are essential to obtain good agreement with experimental results.
Highlights
Nuclear magnetic resonance (NMR) chemical shieldings and quadrupolar couplings provide a means of examining the electronic state of a material
We examine the effect of application of the frozen core approximation (FCA) in calculating NMR chemical shielding using molecular clusters, and we examine the effect of neglect of various parts of the relativistic Hamiltonian in NMR calculations by treating the molecular clusters at different levels of theory
The comparison of results on small clusters with large clusters demonstrates that to predict the NMR chemical shielding accurately, one must take into account the effects of the surrounding environment, and one must treat the problem with a large cluster that maintains symmetry at the site of the nucleus of interest
Summary
Nuclear magnetic resonance (NMR) chemical shieldings and quadrupolar couplings provide a means of examining the electronic state of a material. Very good approximate computational predictions of isotropic NMR parameters for light nuclei such as 13C and 1H in molecules have become routine nowadays, and such calculations of the parameters are often a part of the assignment of spectra.[3,4] Prediction of NMR parameters of heavier nuclei such as 199Hg, 205Tl, and 207Pb is usually limited to prediction of properties of isolated structures in the gas phase[5,6,7,8] and in the solution phase.[8,9,10,11]. The experimentally determined ranges of chemical shieldings (chemical shifts) for heavy nuclei like 199Hg and 207Pb are generally much larger than the ranges for lighter nuclei such as 13C and 1H. The range of experimental principal components for 199Hg in the various materials studied is almost
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
